Why should the loop be flamed at least once during the streak plate procedure?

Ans.

Streak plate procedure is a technique, which is used for the isolation of pure culture of microbes (bacteria) from a mixed population. The inoculum (desired microbe) is streaked onto the agar plate with the help of an inoculating loop.

Inoculating loop may possess some unwanted bacteria that can contaminate the pure culture. Thus, to avoid contamination or to decrease the number of undesired bacteria on the inoculating loop, the loop is sterilized with at least once during the procedure as bacteria would die due to heat.  

ya the other dude is right